Merge "Support bind mounting volumes into other volume's mountpoint." am: 35eb1ae88a am: 1968bd5a1b

Original change: https://android-review.googlesource.com/c/platform/system/vold/+/2189643

Change-Id: I9712ae9dd4965ba0038b0b255294728462a2985a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

VoldNativeService.cpp

@@ -182,11 +182,13 @@ binder::Status VoldNativeService::abortFuse() {
     return translate(VolumeManager::Instance()->abortFuse());
 }
 
-binder::Status VoldNativeService::onUserAdded(int32_t userId, int32_t userSerial) {
+binder::Status VoldNativeService::onUserAdded(int32_t userId, int32_t userSerial,
+                                              int32_t sharesStorageWithUserId) {
     ENFORCE_SYSTEM_OR_ROOT;
     ACQUIRE_LOCK;
 
-    return translate(VolumeManager::Instance()->onUserAdded(userId, userSerial));
+    return translate(
+            VolumeManager::Instance()->onUserAdded(userId, userSerial, sharesStorageWithUserId));
 }
 
 binder::Status VoldNativeService::onUserRemoved(int32_t userId) {

VoldNativeService.h

@@ -38,7 +38,7 @@ class VoldNativeService : public BinderService<VoldNativeService>, public os::Bn
     binder::Status shutdown();
     binder::Status abortFuse();
 
-    binder::Status onUserAdded(int32_t userId, int32_t userSerial);
+    binder::Status onUserAdded(int32_t userId, int32_t userSerial, int32_t sharesStorageWithUserId);
     binder::Status onUserRemoved(int32_t userId);
     binder::Status onUserStarted(int32_t userId);
     binder::Status onUserStopped(int32_t userId);

VolumeManager.cpp

@@ -81,6 +81,7 @@ using android::vold::CreateDir;
 using android::vold::DeleteDirContents;
 using android::vold::DeleteDirContentsAndDir;
 using android::vold::EnsureDirExists;
+using android::vold::GetFuseMountPathForUser;
 using android::vold::IsFilesystemSupported;
 using android::vold::IsSdcardfsUsed;
 using android::vold::IsVirtioBlkDevice;
@@ -424,10 +425,21 @@ void VolumeManager::createEmulatedVolumesForUser(userid_t userId) {
     }
 }
 
-int VolumeManager::onUserAdded(userid_t userId, int userSerialNumber) {
+userid_t VolumeManager::getSharedStorageUser(userid_t userId) {
+    if (mSharedStorageUser.find(userId) == mSharedStorageUser.end()) {
+        return USER_UNKNOWN;
+    }
+    return mSharedStorageUser.at(userId);
+}
+
+int VolumeManager::onUserAdded(userid_t userId, int userSerialNumber,
+                               userid_t sharesStorageWithUserId) {
     LOG(INFO) << "onUserAdded: " << userId;
 
     mAddedUsers[userId] = userSerialNumber;
+    if (sharesStorageWithUserId != USER_UNKNOWN) {
+        mSharedStorageUser[userId] = sharesStorageWithUserId;
+    }
     return 0;
 }
 
@@ -436,6 +448,7 @@ int VolumeManager::onUserRemoved(userid_t userId) {
 
     onUserStopped(userId);
     mAddedUsers.erase(userId);
+    mSharedStorageUser.erase(userId);
     return 0;
 }
 
@@ -914,6 +927,7 @@ int VolumeManager::reset() {
     updateVirtualDisk();
     mAddedUsers.clear();
     mStartedUsers.clear();
+    mSharedStorageUser.clear();
 
     // Abort all FUSE connections to avoid deadlocks if the FUSE daemon was killed
     // with FUSE fds open.

VolumeManager.h

@@ -104,9 +104,11 @@ class VolumeManager {
 
     const std::set<userid_t>& getStartedUsers() const { return mStartedUsers; }
 
+    userid_t getSharedStorageUser(userid_t userId);
+
     int forgetPartition(const std::string& partGuid, const std::string& fsUuid);
 
-    int onUserAdded(userid_t userId, int userSerialNumber);
+    int onUserAdded(userid_t userId, int userSerialNumber, userid_t cloneParentUserId);
     int onUserRemoved(userid_t userId);
     int onUserStarted(userid_t userId);
     int onUserStopped(userid_t userId);
@@ -225,6 +227,8 @@ class VolumeManager {
     std::list<std::shared_ptr<android::vold::VolumeBase>> mInternalEmulatedVolumes;
 
     std::unordered_map<userid_t, int> mAddedUsers;
+    // Map of users to a user with which they can share storage (eg clone profiles)
+    std::unordered_map<userid_t, userid_t> mSharedStorageUser;
     // This needs to be a regular set because we care about the ordering here;
     // user 0 should always go first, because it is responsible for sdcardfs.
     std::set<userid_t> mStartedUsers;

binder/android/os/IVold.aidl

@@ -30,7 +30,7 @@ interface IVold {
     void reset();
     void shutdown();
 
-    void onUserAdded(int userId, int userSerial);
+    void onUserAdded(int userId, int userSerial, int sharesStorageWithUserId);
     void onUserRemoved(int userId);
     void onUserStarted(int userId);
     void onUserStopped(int userId);

model/EmulatedVolume.cpp

@@ -18,6 +18,7 @@
 
 #include "AppFuseUtil.h"
 #include "Utils.h"
+#include "VolumeBase.h"
 #include "VolumeManager.h"
 
 #include <android-base/logging.h>
@@ -68,7 +69,7 @@ EmulatedVolume::EmulatedVolume(const std::string& rawPath, dev_t device, const s
 
 EmulatedVolume::~EmulatedVolume() {}
 
-std::string EmulatedVolume::getLabel() {
+std::string EmulatedVolume::getLabel() const {
     // We could have migrated storage to an adopted private volume, so always
     // call primary storage "emulated" to avoid media rescans.
     if (getMountFlags() & MountFlags::kPrimary) {
@@ -91,6 +92,29 @@ static status_t doFuseBindMount(const std::string& source, const std::string& ta
     return OK;
 }
 
+// Bind mounts the volume 'volume' onto this volume.
+status_t EmulatedVolume::bindMountVolume(const EmulatedVolume& volume,
+                                         std::list<std::string>& pathsToUnmount) {
+    int myUserId = getMountUserId();
+    int volumeUserId = volume.getMountUserId();
+    std::string label = volume.getLabel();
+
+    // eg /mnt/user/10/emulated/10
+    std::string srcUserPath = GetFuseMountPathForUser(volumeUserId, label);
+    std::string srcPath = StringPrintf("%s/%d", srcUserPath.c_str(), volumeUserId);
+    // eg /mnt/user/0/emulated/10
+    std::string dstUserPath = GetFuseMountPathForUser(myUserId, label);
+    std::string dstPath = StringPrintf("%s/%d", dstUserPath.c_str(), volumeUserId);
+
+    auto status = doFuseBindMount(srcPath, dstPath, pathsToUnmount);
+    if (status == OK) {
+        // Store the mount path, so we can unmount it when this volume goes away
+        mSharedStorageMountPath = dstPath;
+    }
+
+    return status;
+}
+
 status_t EmulatedVolume::mountFuseBindMounts() {
     std::string androidSource;
     std::string label = getLabel();
@@ -152,6 +176,59 @@ status_t EmulatedVolume::mountFuseBindMounts() {
         }
     }
 
+    // For users that share their volume with another user (eg a clone
+    // profile), the current mount setup can cause page cache inconsistency
+    // issues.  Let's say this is user 10, and the user it shares storage with
+    // is user 0.
+    // Then:
+    // * The FUSE daemon for user 0 serves /mnt/user/0
+    // * The FUSE daemon for user 10 serves /mnt/user/10
+    // The emulated volume for user 10 would be located at two paths:
+    // /mnt/user/0/emulated/10
+    // /mnt/user/10/emulated/10
+    // Since these paths refer to the same files but are served by different FUSE
+    // daemons, this can result in page cache inconsistency issues. To prevent this,
+    // bind mount the relevant paths for the involved users:
+    // 1. /mnt/user/10/emulated/10 =B=> /mnt/user/0/emulated/10
+    // 2. /mnt/user/0/emulated/0 =B=> /mnt/user/10/emulated/0
+    //
+    // This will ensure that any access to the volume for a specific user always
+    // goes through a single FUSE daemon.
+    userid_t sharedStorageUserId = VolumeManager::Instance()->getSharedStorageUser(userId);
+    if (sharedStorageUserId != USER_UNKNOWN) {
+        auto filter_fn = [&](const VolumeBase& vol) {
+            if (vol.getState() != VolumeBase::State::kMounted) {
+                // The volume must be mounted
+                return false;
+            }
+            if (vol.getType() != VolumeBase::Type::kEmulated) {
+                return false;
+            }
+            if (vol.getMountUserId() != sharedStorageUserId) {
+                return false;
+            }
+            if ((vol.getMountFlags() & MountFlags::kPrimary) == 0) {
+                // We only care about the primary emulated volume, so not a private
+                // volume with an emulated volume stacked on top.
+                return false;
+            }
+            return true;
+        };
+        auto vol = VolumeManager::Instance()->findVolumeWithFilter(filter_fn);
+        if (vol != nullptr) {
+            auto sharedVol = static_cast<EmulatedVolume*>(vol.get());
+            // Bind mount this volume in the other user's primary volume
+            status = sharedVol->bindMountVolume(*this, pathsToUnmount);
+            if (status != OK) {
+                return status;
+            }
+            // And vice-versa
+            status = bindMountVolume(*sharedVol, pathsToUnmount);
+            if (status != OK) {
+                return status;
+            }
+        }
+    }
     unmount_guard.Disable();
     return OK;
 }
@@ -160,6 +237,14 @@ status_t EmulatedVolume::unmountFuseBindMounts() {
     std::string label = getLabel();
     int userId = getMountUserId();
 
+    if (!mSharedStorageMountPath.empty()) {
+        LOG(INFO) << "Unmounting " << mSharedStorageMountPath;
+        auto status = UnmountTree(mSharedStorageMountPath);
+        if (status != OK) {
+            LOG(ERROR) << "Failed to unmount " << mSharedStorageMountPath;
+        }
+        mSharedStorageMountPath = "";
+    }
     if (mUseSdcardFs || mAppDataIsolationEnabled) {
         std::string installerTarget(
                 StringPrintf("/mnt/installer/%d/%s/%d/Android/obb", userId, label.c_str(), userId));

model/EmulatedVolume.h

@@ -52,7 +52,9 @@ class EmulatedVolume : public VolumeBase {
     status_t mountFuseBindMounts();
     status_t unmountFuseBindMounts();
 
-    std::string getLabel();
+    status_t bindMountVolume(const EmulatedVolume& vol, std::list<std::string>& pathsToUnmount);
+
+    std::string getLabel() const;
     std::string mRawPath;
     std::string mLabel;
 
@@ -73,6 +75,9 @@ class EmulatedVolume : public VolumeBase {
     /* Whether to use app data isolation is enabled tor this volume */
     bool mAppDataIsolationEnabled;
 
+    /* Location of bind mount for another profile that shares storage with us */
+    std::string mSharedStorageMountPath = "";
+
     DISALLOW_COPY_AND_ASSIGN(EmulatedVolume);
 };